diff --git a/packages/nodes-base/nodes/Phantombuster/Phantombuster.node.ts b/packages/nodes-base/nodes/Phantombuster/Phantombuster.node.ts
index c0dc784e137..4739e0e58c1 100644
--- a/packages/nodes-base/nodes/Phantombuster/Phantombuster.node.ts
+++ b/packages/nodes-base/nodes/Phantombuster/Phantombuster.node.ts
@@ -216,19 +216,31 @@ export class Phantombuster implements INodeType {
 							const argumentParameters =
 								((additionalFields.argumentsUi as IDataObject)?.argumentValues as IDataObject[]) ||
 								[];
-							body.arguments = argumentParameters.reduce((object, currentValue) => {
+
+							const argumentsObj = argumentParameters.reduce((object, currentValue) => {
 								object[currentValue.key as string] = currentValue.value;
 								return object;
 							}, {});
+
+							// Only set arguments if not empty as per API requirements
+							if (Object.keys(argumentsObj).length > 0) {
+								body.arguments = argumentsObj;
+							}
 							delete additionalFields.argumentsUi;
 
 							const bonusParameters =
 								((additionalFields.bonusArgumentUi as IDataObject)
 									?.bonusArgumentValue as IDataObject[]) || [];
-							body.bonusArgument = bonusParameters.reduce((object, currentValue) => {
+
+							const bonusArgumentObj = bonusParameters.reduce((object, currentValue) => {
 								object[currentValue.key as string] = currentValue.value;
 								return object;
 							}, {});
+
+							// Only set bonusArgument if not empty as per API requirements
+							if (Object.keys(bonusArgumentObj).length > 0) {
+								body.bonusArgument = bonusArgumentObj;
+							}
 							delete additionalFields.bonusArgumentUi;
 						}
 
diff --git a/packages/nodes-base/nodes/Phantombuster/test/Phantombuster.node.test.ts b/packages/nodes-base/nodes/Phantombuster/test/Phantombuster.node.test.ts
new file mode 100644
index 00000000000..519c89b2868
--- /dev/null
+++ b/packages/nodes-base/nodes/Phantombuster/test/Phantombuster.node.test.ts
@@ -0,0 +1,95 @@
+import { NodeTestHarness } from '@nodes-testing/node-test-harness';
+import nock from 'nock';
+
+describe('Phantombuster Node', () => {
+	const credentials = {
+		phantombusterApi: {
+			apiKey: 'test-api-key',
+		},
+	};
+
+	describe('Launch Agent Without Arguments', () => {
+		beforeAll(() => {
+			const mock = nock('https://api.phantombuster.com');
+
+			mock
+				.post('/api/v2/agents/launch', (body) => {
+					return body.id === 'test-agent-123' && !body.arguments && !body.bonusArgument;
+				})
+				.reply(200, { containerId: 'container-456' });
+		});
+
+		new NodeTestHarness().setupTests({
+			credentials,
+			workflowFiles: ['launch-without-arguments.workflow.json'],
+		});
+	});
+
+	describe('Launch Agent With Arguments No Bonus', () => {
+		beforeAll(() => {
+			const mock = nock('https://api.phantombuster.com');
+
+			mock
+				.post('/api/v2/agents/launch', (body) => {
+					return (
+						body.id === 'test-agent-123' &&
+						body.arguments &&
+						body.arguments.testKey === 'testValue' &&
+						!body.bonusArgument
+					);
+				})
+				.reply(200, { containerId: 'container-456' });
+		});
+
+		new NodeTestHarness().setupTests({
+			credentials,
+			workflowFiles: ['launch-with-arguments-no-bonus.workflow.json'],
+		});
+	});
+
+	describe('Launch Agent With Bonus Arguments', () => {
+		beforeAll(() => {
+			const mock = nock('https://api.phantombuster.com');
+
+			mock
+				.post('/api/v2/agents/launch', (body) => {
+					return (
+						body.id === 'test-agent-123' &&
+						body.arguments &&
+						body.arguments.testKey === 'testValue' &&
+						body.bonusArgument &&
+						body.bonusArgument.bonusKey === 'bonusValue'
+					);
+				})
+				.reply(200, { containerId: 'container-456' });
+		});
+
+		new NodeTestHarness().setupTests({
+			credentials,
+			workflowFiles: ['launch-with-bonus-arguments.workflow.json'],
+		});
+	});
+
+	describe('Launch Agent With JSON Arguments', () => {
+		beforeAll(() => {
+			const mock = nock('https://api.phantombuster.com');
+
+			mock
+				.post('/api/v2/agents/launch', (body) => {
+					return (
+						body.id === 'test-agent-123' &&
+						body.arguments &&
+						body.arguments.complexKey === 'complexValue' &&
+						body.arguments.nestedObject &&
+						body.arguments.nestedObject.nested === 'value'
+					);
+				})
+				.reply(200, { containerId: 'container-456' });
+		});
+
+		new NodeTestHarness().setupTests({
+			credentials,
+			workflowFiles: ['launch-with-json-arguments.workflow.json'],
+		});
+	});
+});
diff --git a/packages/nodes-base/nodes/Phantombuster/test/launch-with-arguments-no-bonus.workflow.json b/packages/nodes-base/nodes/Phantombuster/test/launch-with-arguments-no-bonus.workflow.json
new file mode 100644
index 00000000000..bbc1112bcc9
--- /dev/null
+++ b/packages/nodes-base/nodes/Phantombuster/test/launch-with-arguments-no-bonus.workflow.json
@@ -0,0 +1,69 @@
+{
+	"name": "Phantombuster Launch With Arguments No Bonus Test",
+	"nodes": [
+		{
+			"parameters": {},
+			"id": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
+			"name": "When clicking 'Execute Workflow'",
+			"type": "n8n-nodes-base.manualTrigger",
+			"typeVersion": 1,
+			"position": [0, 0]
+		},
+		{
+			"parameters": {
+				"resource": "agent",
+				"operation": "launch",
+				"agentId": "test-agent-123",
+				"jsonParameters": false,
+				"resolveData": false,
+				"additionalFields": {
+					"argumentsUi": {
+						"argumentValues": [
+							{
+								"key": "testKey",
+								"value": "testValue"
+							}
+						]
+					}
+				}
+			},
+			"id": "b2c3d4e5-f6a7-8901-bcde-f12345678901",
+			"name": "Phantombuster",
+			"type": "n8n-nodes-base.phantombuster",
+			"typeVersion": 1,
+			"position": [220, 0],
+			"credentials": {
+				"phantombusterApi": {
+					"id": "test-cred-id",
+					"name": "Phantombuster API"
+				}
+			}
+		}
+	],
+	"pinData": {
+		"Phantombuster": [
+			{
+				"json": {
+					"containerId": "container-456"
+				}
+			}
+		]
+	},
+	"connections": {
+		"When clicking 'Execute Workflow'": {
+			"main": [
+				[
+					{
+						"node": "Phantombuster",
+						"type": "main",
+						"index": 0
+					}
+				]
+			]
+		}
+	},
+	"active": false,
+	"settings": {
+		"executionOrder": "v1"
+	}
+}
diff --git a/packages/nodes-base/nodes/Phantombuster/test/launch-with-bonus-arguments.workflow.json b/packages/nodes-base/nodes/Phantombuster/test/launch-with-bonus-arguments.workflow.json
new file mode 100644
index 00000000000..41a1afd0959
--- /dev/null
+++ b/packages/nodes-base/nodes/Phantombuster/test/launch-with-bonus-arguments.workflow.json
@@ -0,0 +1,77 @@
+{
+	"name": "Phantombuster Launch With Bonus Arguments Test",
+	"nodes": [
+		{
+			"parameters": {},
+			"id": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
+			"name": "When clicking 'Execute Workflow'",
+			"type": "n8n-nodes-base.manualTrigger",
+			"typeVersion": 1,
+			"position": [0, 0]
+		},
+		{
+			"parameters": {
+				"resource": "agent",
+				"operation": "launch",
+				"agentId": "test-agent-123",
+				"jsonParameters": false,
+				"resolveData": false,
+				"additionalFields": {
+					"argumentsUi": {
+						"argumentValues": [
+							{
+								"key": "testKey",
+								"value": "testValue"
+							}
+						]
+					},
+					"bonusArgumentUi": {
+						"bonusArgumentValue": [
+							{
+								"key": "bonusKey",
+								"value": "bonusValue"
+							}
+						]
+					}
+				}
+			},
+			"id": "b2c3d4e5-f6a7-8901-bcde-f12345678901",
+			"name": "Phantombuster",
+			"type": "n8n-nodes-base.phantombuster",
+			"typeVersion": 1,
+			"position": [220, 0],
+			"credentials": {
+				"phantombusterApi": {
+					"id": "test-cred-id",
+					"name": "Phantombuster API"
+				}
+			}
+		}
+	],
+	"pinData": {
+		"Phantombuster": [
+			{
+				"json": {
+					"containerId": "container-456"
+				}
+			}
+		]
+	},
+	"connections": {
+		"When clicking 'Execute Workflow'": {
+			"main": [
+				[
+					{
+						"node": "Phantombuster",
+						"type": "main",
+						"index": 0
+					}
+				]
+			]
+		}
+	},
+	"active": false,
+	"settings": {
+		"executionOrder": "v1"
+	}
+}
diff --git a/packages/nodes-base/nodes/Phantombuster/test/launch-with-json-arguments.workflow.json b/packages/nodes-base/nodes/Phantombuster/test/launch-with-json-arguments.workflow.json
new file mode 100644
index 00000000000..243b8eb2f39
--- /dev/null
+++ b/packages/nodes-base/nodes/Phantombuster/test/launch-with-json-arguments.workflow.json
@@ -0,0 +1,62 @@
+{
+	"name": "Phantombuster Launch With JSON Arguments Test",
+	"nodes": [
+		{
+			"parameters": {},
+			"id": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
+			"name": "When clicking 'Execute Workflow'",
+			"type": "n8n-nodes-base.manualTrigger",
+			"typeVersion": 1,
+			"position": [0, 0]
+		},
+		{
+			"parameters": {
+				"resource": "agent",
+				"operation": "launch",
+				"agentId": "test-agent-123",
+				"jsonParameters": true,
+				"resolveData": false,
+				"additionalFields": {
+					"argumentsJson": "{\"complexKey\":\"complexValue\",\"nestedObject\":{\"nested\":\"value\"}}"
+				}
+			},
+			"id": "b2c3d4e5-f6a7-8901-bcde-f12345678901",
+			"name": "Phantombuster",
+			"type": "n8n-nodes-base.phantombuster",
+			"typeVersion": 1,
+			"position": [220, 0],
+			"credentials": {
+				"phantombusterApi": {
+					"id": "test-cred-id",
+					"name": "Phantombuster API"
+				}
+			}
+		}
+	],
+	"pinData": {
+		"Phantombuster": [
+			{
+				"json": {
+					"containerId": "container-456"
+				}
+			}
+		]
+	},
+	"connections": {
+		"When clicking 'Execute Workflow'": {
+			"main": [
+				[
+					{
+						"node": "Phantombuster",
+						"type": "main",
+						"index": 0
+					}
+				]
+			]
+		}
+	},
+	"active": false,
+	"settings": {
+		"executionOrder": "v1"
+	}
+}
diff --git a/packages/nodes-base/nodes/Phantombuster/test/launch-without-arguments.workflow.json b/packages/nodes-base/nodes/Phantombuster/test/launch-without-arguments.workflow.json
new file mode 100644
index 00000000000..4b54542770c
--- /dev/null
+++ b/packages/nodes-base/nodes/Phantombuster/test/launch-without-arguments.workflow.json
@@ -0,0 +1,59 @@
+{
+	"name": "Phantombuster Launch Without Arguments Test",
+	"nodes": [
+		{
+			"parameters": {},
+			"id": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
+			"name": "When clicking 'Execute Workflow'",
+			"type": "n8n-nodes-base.manualTrigger",
+			"typeVersion": 1,
+			"position": [0, 0]
+		},
+		{
+			"parameters": {
+				"resource": "agent",
+				"operation": "launch",
+				"agentId": "test-agent-123",
+				"jsonParameters": false,
+				"resolveData": false
+			},
+			"id": "b2c3d4e5-f6a7-8901-bcde-f12345678901",
+			"name": "Phantombuster",
+			"type": "n8n-nodes-base.phantombuster",
+			"typeVersion": 1,
+			"position": [220, 0],
+			"credentials": {
+				"phantombusterApi": {
+					"id": "test-cred-id",
+					"name": "Phantombuster API"
+				}
+			}
+		}
+	],
+	"pinData": {
+		"Phantombuster": [
+			{
+				"json": {
+					"containerId": "container-456"
+				}
+			}
+		]
+	},
+	"connections": {
+		"When clicking 'Execute Workflow'": {
+			"main": [
+				[
+					{
+						"node": "Phantombuster",
+						"type": "main",
+						"index": 0
+					}
+				]
+			]
+		}
+	},
+	"active": false,
+	"settings": {
+		"executionOrder": "v1"
+	}
+}